THE ORIGIN AND EVOLUTION OF DINOSAURS

Phylogenetic studies and new fossil evidence have yielded fundamental insights into the pattern and timing of dinosaur evolution and the eme rgence of functionally modern birds. The dinosaurian radiation began i n the Middle Triassic, significantly predating the global dominance of dinosaurs by the end of the period. The phylogenetic history of ornit hischian and saurischian dinosaurs reveals evolutionary trends such as increasing body size. Adaptations to herbivory in dinosaurs were not tightly correlated with marked floral replacements. Dinosaurian biogeo graphy during the era of continental breakup principally involved disp ersal and regional extinction.